Sunday sands

February 24, 2013

There’s only one major sand dune field on the Colorado Plateau, and that can
be found at the Coral Pink Sand Dunes State Park, way down in the southwest
corner of Utah, not far from Zion National Park. And are these dunes really
coral pink? Or reddish orange? Or orangey pink? Opinions vary – as do the
colours of the sand depending on the light and the time of day. But their true
colour hardly matters – they are impressive dunes.

Formed perhaps 10,000 years ago, as the northern ice
was beginning to recede, their sands are home to a diversity of plants and
animals, including the charming – but severely threatened – Coral Pink Sand
Dunes tiger beetle, Cicindela albissima, only recently promoted to a
species in its own right, and which is only found in these dunes.

The sand grains are typical of a windblown heritage, smoothed, frosted, and
rounded by the endless mutual abrasion as they are buffeted by the wind. And
they are all more or less of the same size – the finer grains are blown onwards,
the coarser ones left behind; and they are essentially all quartz.

It’s the local winds that explain why these dunes are where they are. Just to
the north-east of the dunes is a significant “notch” in the ranges of the
plateau. The prevailing winds blast sand south-westwards, are funnelled through
the notch, and, as they emerge and diminish, can no longer carry the sand,
dropping it to feed the dunes. If you look at this on Google Earth, you can
almost feel the sands streaming through the gap in the hills:

And why is that gap there? Well, because one of the great geo-architectural
features of the Colorado Plateau, the Sevier Fault, cuts through it. The fault
is a huge fracture in the earth’s crust, over a hundred kilometres long, and
almost vertical; everything to the west of the fault has dropped down 700 meters
(2300 feet) relative to the rocks on the east. The fault is clearly visible on
the satellite image below, right, as a scar slicing across the landscape:

On the left is exactly the same area but shown as a geological map, the rocks
of different ages appearing in different colours, the faults as black lines. To
the east of the Sevier fault, the landscape is dominated by the light blue rocks
of the Navajo Sandstone, to the west, the green of the Carmel Formation, mostly
made up of limestones. The Navajo was deposited during the Lower Jurassic,
around 185 million years ago, the Carmel later, on top of it, around 165 million
years ago. So the map shows clearly that the movement on the Sevier fault is
down to the west – the rocks of the Carmel are younger than the Navajo in the
hills to the east, and have been completely removed by erosion on the uplifted
side of the fault.

It’s a big and complex fault system, and the grinding of fault movement would
have pulverised the rock along the fault zone, leaving it weaker and exposed to
erosion – hence the gap through which the sands blow. And the Sevier fault is
still on the move – it has been seismically active for a long time, part of the
so-called intermontane
seismic belt.

So, we have figured out why all those sand grains are piled up where they
are, but what’s their story? The photo below shows the dunes in the foreground
and, in background, the pink sandstones of the Navajo Sandstone on the east side
of the fault. Look carefully and you will recognise dunes ancient and
modern.

The Navajo is an iconic formation, the star of the landscapes of many
of Utah’s national and state parks. It represents an enormous erg, a large sand
sea that extended over most of Utah as well as parts of New Mexico, Arizona,
Colorado and Wyoming. Look carefully at the bluffs in the photo, and you can see
gigantic scale cross-bedding, signalling wind-blown sand, dunes. Excavate
the dunes of the Coral Pink Sand Dunes (in your imagination), and exactly the
same structures will be revealed – the vital principle of uniformitarianism at
work. That principle derives from the observations of James Hutton in the late
18th century, that the processes we see today sculpting the surface of our
planet have always operated, and always will. Commonly summarised as “the
present is the key to the past,” it has been debated and refined ever since –
for example, the rates at which a process, e.g., global
volcanism, operated have varied over time – but the principle is, indeed, the
key to our being able to read the ledgers of earth’s history. Winds have always
blown, sand has always been on the move, dunes have always been built in the
same way.

The bluffs of ancient Navajo dunes in south-western Utah have been exposed to
the attack of weathering and erosion for a long time, disintegrating and
liberating the tough little sand grains. Those grains have been swept along by
rivers, left in sand banks, dried out, and picked up by the wind for the next
stage of their travels – to the Coral Pink Sand Dunes State Park. There they
rest, for a while, on their never-ending journey, and what you see in those
dunes today are re-cycled grains from a desert nearly two hundred million years
ago.

[Heartfelt thanks to Myrna and Charles Gifford for collecting and sending the sand,
and for the photographs.

December 09, 2012

Blustery. A wonderful, quintessentially English adjective, for
quintessentially English weather. “Blustery conditions will continue along the
coast for the next few days.” Weeks? Months?

Well, it was November when we ventured to the Lake District at the kind
invitation of the Cumberland Geological Society, and so we should hardly have
been surprised by the weather – downpours in the hills, blustery on the coast.
But blustery does make for drama – breaks in the fast-moving clouds, bursts of
sun as well as rain. A walk along the beach, to use another quintessentially
English term, “bracing.”

The goal was to have a look at the only cliffs of any significance between
Wales and Scotland, the headland at St. Bees. The headland is underpinned by the
St. Bees Sandstone, a gloriously red sequence of river sands and gravels,
together with the occasional dune, recording the time 250 million years ago when
Europe and North America no longer saw eye-to-eye and began rifting apart. The
dynamics and vigour of these rivers is recorded in the swirling cross-bedding
and intervening floods of pebbles in the cliffs.

The St. Bees Sandstones have been much prized for building, not only locally,
but, as ballast in transatlantic ships, found their way into U.S. buildings –
coals to Newcastle, really, since the iconic brownstones are of the same age and
origin. And there’s another transatlantic connection – just up the coast from
St. Bees is the old port of Whitehaven, scene of the
U.S. invasion in 1778.

The sand grains of the St. Bees are fine-grained, angular and abrasive, their
iron oxide coatings distinguishing them dramatically from the beach sands that
reflect the rivers working away at the rocks of the Lake district and Southern
Scotland. Where a small gully washed the local ingredients from the cliffs down
on to the beach, the contrast was striking, a comparison amplified under the
microscope:

One of the positives of arenophilia is that it provides destinations, often
off the beaten track, small, oddball journeys through geography and history that
would otherwise remain untaken. Our blustery afternoon stroll on the Cumbrian
coast is a great example – and was further inspired by the wonderful contemplation
of the St. Bees Sandstone by my writer/weaver friend, Ann Lingard, on her
Solway Shore Stories website. And enjoy again her guest
post from a couple of years ago.

Finally, a note: this will complete posting for 2012, and I wish my readers
the very best for the holiday season and 2013. And, in the New Year, posting may
well become more sporadic – I have another book to write, and am already on the
verge of panic. However, we’ll see how things work out – this is my 400th post,
and perhaps time to wander off in quest of a few laurels to rest on.

September 09, 2012

I was delighted (but envious) when my friend Patricia brought me back a
sample of sand from her recent visit to Bhutan. The sand came from one of the
country’s most sacred places (and its old capital), Punakha, at the confluence
of two great rivers, the Mo Chu (the mother river) and the Pho Chu (the father).
The Palace, the Punakha Dzong, is also known as Pungtang Dechen Photrang Dzong,
the palace of great happiness, and this magnificent structure originally dates
from the 17th century. But happiness has not reigned continuously during its
long history. It has been re-built many times over the centuries after fires and
earthquakes, and it is regularly threatened by floods, the most recent severe
event occurring in 1994.

And there’s a good reason for the floods, created not by the mother river,
but by the father. Follow the Pho Chu upstream from Punakha, and you climb
rapidly into the high Himalayas, towards the snow caps, the ice fields, and the
glaciers that provide the source of the river. Now glaciers are environmentally
careless, dumping and reworking the great loads of rock and sediment that they
carry with no regard for landscape maintenance. The great piles of glacial
litter that remain (moraines) can often act as dams for the glacial melt water,
and lakes build up behind them. In the lower images, below, there are four
glaciers feeding the upper reaches of the valley down which the Pho Chu
flows:

Partly frozen in the image on the left, open and melted on the right, are a
series of such glacial lakes. Most of the time, such lakes are benign, simply
adding an extra element to the grandeur of glaciated mountains anywhere in the
world. However, as the Nova
article on glacier hazards notes, “Once such a lake has formed, melting
and retreat of the glacier front accelerates because water transports heat much
more efficiently to the ice front than air can.” And, ultimately, that’s when a
benign landform can turn nasty. The natural dams reach the point that they can
no longer hold back the waters accumulating behind them, and burst, letting
loose a massive torrent of floodwaters charging down the valley. Such was the
case on October 7th, 1994, with the lake, Lugge Tso, seen clearly in the
satellite images. Also clearly visible is the breach in the moraine dam and
the flood channel downstream of it. Such an event is known in the trade as a
glacial lake outburst flood, or “GLOF.”

At Punakha, the typical average river flow is perhaps a couple of hundred
cubic meters – around a thousand bath tubs – per second. In October 2004, the
peak river flow measured downstream from Punakha, and more than a
hundred kilometres from the lake, was 2500 cubic meters per second. And
this is what Punakha looked like (with a normal view for comparison):

The father river has adopted a second channel, and unimaginable tons of sand
are being re-distributed along the valley – a re-sculpturing of the landscape that
will change everything for the flow of the river in both normal times and flood.
But there are man-made changes in the works, too – given that there are another
2500 glacial lakes besides Lugge Tso in the Bhutan Himalayas, a grand scheme is
underway. The defences put in place after the 1994 flood are regarded as
inadequate, and the current project is to move the confluence of the mother and
father rivers 300 meters downstream of its present location:

The department of geology and mines (DGM) has a proposal to divert the Phochu
and Mochu rivers to protect Punakha dzong in case of a glacial lake overflow
flood (GLOF) and cyclone floods.

It proposes moving the confluence of the two rivers more than 300 m
downstream. “We’ve sent to the dzongkhag an estimate of Nu 508,310 to survey
and study the river basin area,” said Ugyen Wangda, chief geologist of DGM. If
approved, construction would take around three years.

The present defenses of the Punakha dzong, built after the 1994 floods, can
withstand only 18 million cubic metres (cu m), according to DGM. “The proposed
diversion will protect the dzong from even a 53 million cu m flood, if the
Lunana lakes of Rapstreng and Thorthormi burst,” said Ugyen Wangdi.

The proposal came up in a May 2009 home ministry meeting after the GLOF false
alarm in Punakha, when an underground lake in Tshojo glacier had burst. “The
main concern was on how to evacuate the holy relics of the Ranjung Kharsapani
and the Machen to a safer place,” said Ugyen.

The main danger is from the headwater of Phochu, where there is a chance of
GLOF, if the Rapstreng and Thorthormi lakes overflow into each other, according
to DGM.

“We plan to divert the Phochu two or three kilometres before the dzong and
take it over the paddy fields, which are currently on the left banks,” said
Ugyen.

A kilometre long and three metres broad giant wall could be built further
away from the dzong’s current wall. The enlarged area, behind the wall, is
proposed to be converted into a large park. “If there is GLOF and the river
overflows its banks, there should be no impact as the river basin will be very
large,” said Ugyen Wangdi.

The classic and spectacular view of the Palace of Great Happiness will be
consigned to history.

But back to the sand. These are raw, young grains, only recently ripped out
of their Himalayan parent-rocks, tumbled downstream by everyday river flow and
the occasional GLOF, witnesses to violence, but barely changed from their
original crystal forms. Another lovely sand - thanks, Patricia.

[This is the second time I have been fortunate to have a Bhutan sample for
the Sunday Sand series – see the
other one here.]

{A very good summary of GLOFs of the Bhutan Himalayas: Chhopel, Karma
(2006-03-15). "Flash
Floods and Debris Flows due to Glacial Lake Outburst Floods" (ppt).
Proceedings of the International Workshop on Flash Flood Forecasting
coordinated by the U.S. National Oceanic and Atmospheric Administration's
National Weather Service and the World Meteorological Organization, San José,
Costa Rica, March 2006.

August 26, 2012

Heralded as one of the finest beaches in the world, Unawatuna lies close to
the southern tip of Sri Lanka. The sand contributes to the heralding – on every
scale – but this sand must have tales to tell. The resort was devastated by the
2004 tsunami, and a quick search of the internet reveals harrowing stories
typical of those from around the Indian Ocean that appalling day. The before and
after images below do not begin to evoke the full extent of the catastrophe that
hit the residents that day, but the Google Earth image (from before the
tsunami) shows the complex way in which the shape of the coast refracts and
focuses even normal ocean waves – the chaos of what this natural lens created
when successive tsunami surges hit can only be imagined.

Many stretches of Sri Lanka’s beaches lost huge amounts of sand, but nature
seems to have achieved effective beach nourishment and restoration. I can find
no evidence of a human contribution to the re-supply of sand, only the
opposite – extensive sand mining that reduced the coastal supply and inhibited
the natural processes. So who knows exactly what stories these sand grains
tell? In all likelihood some were sucked from the beach, only to be thrown back
as the tsunami surged, joined probably by others that had been residing
peacefully offshore, among the coral reefs whose fragments we see in the sand.
But this is a spectacular and diverse sand: the ubiquitous quartz grains there,
but overwhelmed by biogenic detritus. Sponge spicules, coral fragments, sea
urchin spines, the inevitable forams,
bits and pieces of shells as well as tiny complete ones, all testimony to the great organic engine of the
tropical ocean. And what exactly that little beautiful blue and grey “cogwheel”
is, I really don’t know.

All in all, a sand and a beach whose character belies their witness to chaos
and tragedy.

[Thanks – once again – to Connie for collecting the sand. The immediate
post-tsunami image is from Muddled Clarity, the tranquil beach scene from HolidayCheck.com]

July 14, 2012

Georgia Bore is the place along the Canning Stock Route where we spent more time than planned - thanks to the mechanical failure of our primary four-wheel-drive vehicle. But there are far worse places to be stranded, not only in terms of being able to arrange being de-stranded, but it's also in the midst of spectacular landscapes - including those of the long, seemingly endless, dunes that striate the western deserts of Australia. And the "Bore" refers to the drilled well at the location, a piece of good fortune, since we were never short of water during our sojourn there.The name "Georgia" originates from a tradition in the company that drilled the well that each of their camps should be named after the most recently born child of individuals working on the project: Georgia was the daughter of the senior geologist.

Having a little time on my hands to explore, I wandered, predictably, around the dunes. Like seemingly everything in Australia, they're different. Not only kilometres long, not only vegetated, but the sand itself is not exactly typical of a standard desert dune. If you look at the grains of an Egyptian dune, they bear all the classic hallmarks of long periods of aeolian work: smoothed and rounded, frosted by the impacts with their brethren, and all much of a muchness in terms of size. But most of these antipodian grains, while clearly showing signs of having been knocked around, are still quite angular, and the variation in grain size is considerable. Does this suggest that their story is a fast and furious one, relatively brief but hyper-active periods of extreme aridity, punctuated by long periods of stability? I'm not sure - any suggestions?

July 01, 2012

Playas, creekbeds, dunes, hills. The interior of Australia was popularly referred to in the nineteenth century as "the ghastly blank." It remains in reality a harsh land, but one of extraordinary beauty and breath-taking diversity.

May 19, 2012

Pelabuhan Ratu, a sweeping beach on the south coast of Java pounded continuously by the breakers of the Indian Ocean. A popular destination, but one that I have not visited – today’s feature comes courtesy of, and with thanks to, Carol Banks, the latest recruit to my growing army of sand-snatchers.

Pelabuhan Ratu means “Queen’s harbour,” and the place comes with myths and legends galore – but more of that later: for now, the sand. The most popular and developed part of the long beach is a typical tropical white, but great stretches are also gloomily black and less attractive – except to an arenophile, for this is a lovely sand.

I chose the Google Earth image above to show the less-developed section, the river clearly bringing its cargo of black sands down to the coast. When the sand is wet, it is truly a dark charcoal-grey colour, but dry it out and it takes on a speckled brown and grey character – not particularly attractive at first glance. But look closely, and you will see transparent quartz grains, glittering like diamonds amongst the dull fragments of dark volcanic rock. Then there are the grains of the local limestones, together with a few shell fragments, shattered by the surf.

Looking more closely, those grains of transparent volcanic quartz really are beautiful:

A number of them, dramatically the one at the upper right, show conchoidal fractures. These are where a material breaks along curved surfaces, often complex and rippled, very much the form of a mussel shell, hence the name (from the Greek for mussel or cockle). This behaviour is typical of amorphous materials such as glass and its natural volcanic version, obsidian – it’s this kind of fracturing that is exploited in the making of obsidian and flint tools. Strictly amorphous materials such as glass have no internal structure to guide fractures; this is not true of quartz, but its mineral structure, and the strength of the bonds between the silicon and oxygen atoms, make it behave very much as if it were amorphous.

The apple-green jewels amongst the grains are the mineral olivine, a common constituent of the kinds of volcanic materials of which Java is constructed. Shine the microscope light through the sand, and the glowing glory of these grains is revealed:

But, in the first group of microscope photos above, there are also very distinctive tiny black grains, clustering together, looking vaguely metallic, and often of a very regular, geometric, shape. What are they? Well, the answer is easily discovered by passing a magnet over the surface of the sand – these little grains defy gravity and hurl themselves upwards on to the magnet’s surface, reasonable behaviour for magnetite.

Magnetite is an iron oxide, chemical formula Fe3O4, and is another common constituent of the local volcanic rocks; it’s the most magnetic of all minerals, and is the key to the lodestone, used for early compasses. Left free to fulfil its ambitions, magnetite can form large clusters of glorious crystals such as this specimen, up to ten centimetres across, from one of the mines in St. Lawrence County New York, and in the collection of the New York State Academy of Mineralogy. Unfortunately, since it is a valuable source of iron, magnetite has a social dark side: because it is heavy, the waves of the beach concentrate the grains into placer deposits, and, along the south coast of Java these have been the source of sometimes violent conflicts between developers and local farming communities. But back to the bright side of magnetite, so to speak.

Because these grains do form placer deposits, a little amateur panning in the kitchen separated them out from the lighter grains (I could, of course, have used my magnet, but that wouldn’t have been so much fun). Here are some family portraits:

The amazing thing is that so many of these grains are hardly worn at all, and their original crystal shape is preserved. Look at the one that seems like two pyramids stuck together – that’s the original octohedral form of the mineral, a single, almost perfect, crystal of magnetite. Raw diamonds are often octohedral, but these grains are just humble iron oxide – beautiful nevertheless, don’t you think?

So, what about the queen whose harbour, or bay, is Pelabuhan Ratu? Well, this stretch of the Java coast is the haunt of Nyai Roro Kidul, the mythical Queen of the Indian Ocean in these parts, and a shape-shifting spirit of Javanese and Sundanese folklore. She is, of course, beautiful, but she is powerful, able to take your soul on a whim. Various versions of the legend describe how a beautiful princess was struck with black magic by a jealous rival in the palace and developed a horrible skin disease. She fled to the ocean and plunged into the waves, where she was cured and crowned queen by the marine spirits and demons. Her sacred colour is green, and there is a local belief that wearing green will anger Nyai Roro Kidul – so, arenophiles, should you visit Pelabuhan Ratu, please choose your outfit with this in mind.

April 21, 2012

For the last 15 years, on and off, I have been collecting sand. The “off” times resulted from not having an answer to the question, ‘what do I do with all of this sand?’ I have tried various methods of displaying my sands as you can see below. Two-ounce bottles with overhead lighting being the best.

But the only people who could regularly view the display were my wife, the neighbors, some family and my dog, Zena, and she could care less. In fact, anything that draws attention away from her is not well tolerated.

Things got interesting again, however, when I decided to try my hand at getting pictures of my sands. At first, I tried a digital microscope and although it turned out to be an interesting exercise, the quality just wasn’t there. The edges, for example, are usually blurry, the definition is often lacking and the color is rarely true. These problems would even be too much for a Photoshop package. You can, however, get a good idea of what is lurking in your sand sample at 20x, as in this image of sand from Fintragh beach, but it is not suitable for framing.

Today I still use the digital microscope but only for screening sand samples. It is pretty good at predicting which sands will be “photogenic.”

My first foray into serious sand macrophotography began with my purchase of a used Nikon D70. The following picture was taken with that camera body and a 60mm 1:1 lens. Even though the sensor is only a 6.1MP it still provides a pretty good image. This photo is of one of the famous green sand beaches in Hawaii, Pocket Beach to be exact. The olivine, lava and coral make a striking image [at the head of this post - MW].

At any rate, this new photographic endeavor answered the big question, ‘what do I do with all of this sand?’ Answer, SHOOT IT.

There are a number of photographers who do outstanding sand photography. I would like to showcase several of them. This is, by no means, an exhaustive list. This only reflects the photographers that have posted images on my website, Tropics of Sand. I will attempt to compare and contrast their styles. As you will see, the top photographers all have their own style. Over and above the camera equipment used, the thing that defines a photographer is their approach to getting the shot. All of the images that you will see below are unique to the photographer. I can tell a Heider photo from a Couette and a Sepp from a Kenney in the blink of an eye. I am sure that you will, too.

SAND PHOTOGRAPHERS

(click images to enlarge)

Leo Kenney: Large field, great clarity

Leo is a veteran of creating outstanding sand calendars and posters. He has a prodigious collection thanks to the fact that he has a legion of former students who dutifully send sands to him from their travels (cheater). Leo tends to zoom out a bit which produces a larger field than most. He uses a Canon 1-5x lens that allows him to get that clarity. Leo’s Picasa Web albums are here.

Siim Sepp: Great definition of full field shots and individual grains.

Siim also uses the Canon 1-5x lens although Siim does more close up work. He uses a full field for some of his photos but he also shows exploded views of individual grains of sand elements. Siim has a “how-to” on the mechanics of getting a sand photo on his website, Sand Atlas. On that site, he also provides geological information on sand composition that is very informative.

Herr Heider gets excellent close ups of his sands without sacrificing detail. As you can see in this series of sands from Ireland he is able to keep detail at close range. He also agonizes over white balance which gives very exacting color to his images. His tight shots and true color make his photos stand out.

Alain will not reveal what he uses as a lighting source but whatever it is, it gives his photos a “soft” look and it is also rich in detail. Alain has numerous images on his website, Arénophile ou Psammophile? He has sand pix plus images of forams that are very interesting. Alain has a distinctive style that I would recognize anywhere.

Carla is one of the pre-eminent sand photographers today. As you can see her shots are very rich in detail. This is not due to the lens but the fact she shoots her photos in daylight, the sun illuminating every nook and cranny which in turn provides outstanding definition. The other thing that separates Carla from the pack is her prodigious collection. She has sand from anywhere you can imagine which greatly increases the chances of having outstanding material to work with. Below are 4 shots that typify her style, and of course, no examination of Carla’s work would be complete without a sample of one of her “selections”. These are selected bits of coral, forams, shells, etc., from various sand samples. I hesitate to use more than one for the simple reason that they are too awesome. If you can look at these all day, why would you look at anything else?

I now use a Nikon d1500 with the same 60mm lens. What I like to do with my photos is create an edge where heavy minerals or carbonate elements can be isolated from the main body of sand allowing for a better view of the individual grains. This has been dubbed the “black corner” technique. The 5100 has a 16.2 MP sensor that will enable you to enlarge photos without losing definition. Also, I use black or other colored glass as a background to provide contrast.

Kurt is based in Pennsylvania, and writes that while he has been photographing sand for the last three years, he has collected it for “15 odd years.” Nothing odd about that as far as I’m concerned, but perhaps those years were odd in other ways, and sand collecting represented an opportunity for normality. Interestingly, he enjoys diving for samples. Anyway, thanks Kurt for all the effort in putting this together – and thanksto all the arenophile photographers who contributed to this piece.]

April 08, 2012

Sand from perhaps the smallest “beach” that I have visited and sampled. One of the items on the varied agenda of a recent long weekend in Central Java (varied in the way that part of the world uniquely and fascinatingly offers) was an exploration of a few of the small beaches on Java’s south coast. My intention was to avoid the crowds at the large, popular, beaches (the day of the visit being Sunday) and find a couple of the small coves that nestle between the spectacular cliffs of that part of the coast. The first destination was Ngobaran – and it certainly fulfilled the criterion of a “small beach.” Dramatic and rugged limestone cliffs face the incoming waves of the Indian Ocean, and the constant kinetics of the place leave little opportunity for sand grains to gather. But, in a small area sheltered by massive boulders, a patch of coarse sand had accumulated:

And here it is, the usual mix of local ingredients, including many of the little spherical forams, so common in these parts and looking for all the world like natural ball-bearings:

In detail, the varied patterns and textures are endless:

And, as further geo-entertainment, the weathering of the limestone boulders produced a starkly rugged form of tafoni:

And, as I watched the Indian Ocean waves roll in, I was inspired to play with the the high-speed burst function of my camera and experiment with catching the action – nothing to do directly with sand, so please excuse my self-indulgence: